U.S. patent application number 16/065858 was filed with the patent office on 2020-09-10 for line beam light source, line beam irradiation device, and laser lift off method.
The applicant listed for this patent is HON HAI PRECISION INDUSTRY CO., LTD. Invention is credited to KATSUHIKO KISHIMOTO.
Application Number | 20200287356 16/065858 |
Document ID | / |
Family ID | 1000004902039 |
Filed Date | 2020-09-10 |
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United States Patent
Application |
20200287356 |
Kind Code |
A1 |
KISHIMOTO; KATSUHIKO |
September 10, 2020 |
LINE BEAM LIGHT SOURCE, LINE BEAM IRRADIATION DEVICE, AND LASER
LIFT OFF METHOD
Abstract
A line beam irradiation apparatus (1000) includes a work stage
(200), a line beam source (100) for irradiating a work (300) placed
on the work stage (200) with a line beam; and a transporting device
(250) for moving at least one of the work stage (200) and the line
beam source (100) such that an irradiation position of the line
beam on the work moves in a direction transverse to the line beam.
The line beam source includes a plurality of semiconductor laser
devices and a support for supporting the plurality of semiconductor
laser devices. The plurality of semiconductor laser devices are
arranged along a same line extending in a fast axis direction, and
the laser light emitted from emission regions of respective ones of
the semiconductor laser devices diverge parallel to the same line
to form the line beam.
Inventors: |
KISHIMOTO; KATSUHIKO;
(Osaka, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HON HAI PRECISION INDUSTRY CO., LTD |
New Taipei |
|
TW |
|
|
Family ID: |
1000004902039 |
Appl. No.: |
16/065858 |
Filed: |
July 21, 2016 |
PCT Filed: |
July 21, 2016 |
PCT NO: |
PCT/JP2016/071345 |
371 Date: |
June 25, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S 5/0228 20130101;
B23K 26/57 20151001; H01S 5/06233 20130101; B23K 26/032 20130101;
B23K 26/0736 20130101; H01S 5/4075 20130101 |
International
Class: |
H01S 5/40 20060101
H01S005/40; B23K 26/57 20060101 B23K026/57; H01S 5/062 20060101
H01S005/062; H01S 5/022 20060101 H01S005/022; B23K 26/073 20060101
B23K026/073; B23K 26/03 20060101 B23K026/03 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 25, 2015 |
JP |
2015-253586 |
Claims
1. A line beam irradiation apparatus comprising: a work stage; a
line beam source for irradiating a work placed on the work stage
with a line beam; and a transporting device for moving at least one
of the work stage and the line beam source such that an irradiation
position of the line beam on the work moves in a direction
transverse to the line beam, wherein the line beam source includes
a plurality of semiconductor laser devices and a support for
supporting the plurality of semiconductor laser devices, each of
the plurality of semiconductor laser devices includes a
semiconductor multilayer stack which has a facet, the facet
including an emission region from which laser light is to be
emitted, the emission region having a size in a fast axis direction
that is parallel to a layer stacking direction of the semiconductor
multilayer stack and a size in a slow axis direction that is
perpendicular to the layer stacking direction, and the plurality of
semiconductor laser devices are arranged along a same line
extending in the fast axis direction, and the laser light emitted
from the emission regions of respective ones of the plurality of
semiconductor laser devices diverge parallel to the same line to
form the line beam.
2. The line beam irradiation apparatus of claim 1, wherein the size
in the slow axis direction of the emission region is not less than
50 times the size in the fast axis direction of the emission
region.
3. The line beam irradiation apparatus of claim 1, wherein a
distance between centers of arbitrary two of the plurality of
semiconductor laser devices adjoining in the fast axis direction is
not less than 20 mm.
4. The line beam irradiation apparatus of claim 1, wherein the
laser light emitted from the emission region of each of the
plurality of semiconductor laser devices are not collimated in the
fast axis direction.
5. The line beam irradiation apparatus of claim 1, further
comprising an optical member for collimating or converging in the
slow axis direction the laser light emitted from the emission
region of each of the plurality of semiconductor laser devices.
6. The line beam irradiation apparatus of claim 1, further
comprising an actuator for oscillating or moving the plurality of
semiconductor laser devices in the fast axis direction.
7. The line beam irradiation apparatus of claim 1, further
comprising a laser diode driving circuit for driving the plurality
of semiconductor laser devices.
8. The line beam irradiation apparatus of claim 7, wherein the
laser diode driving circuit drives each of the plurality of
semiconductor laser devices.
9. The line beam irradiation apparatus of claim 8, wherein the
laser diode driving circuit drives the plurality of semiconductor
laser devices such that a spatial intensity distribution of the
line beam is modulated.
10. The line beam irradiation apparatus of claim 9, further
comprising a sensor for detecting a structure or state of the work,
wherein the laser diode driving circuit temporally changes the
spatial intensity distribution of the line beam based on the
structure or state of the work detected by the sensor.
11. The line beam irradiation apparatus of claim 10, wherein the
sensor is an image sensor.
12. The line beam irradiation apparatus of claim 1, wherein the
line beam source includes a plurality of auxiliary semiconductor
laser devices supported by the support, each of the plurality of
auxiliary semiconductor laser devices includes a semiconductor
multilayer stack which has a facet, the facet including an emission
region from which laser light is to be emitted, the emission region
having a size in a fast axis direction that is parallel to a layer
stacking direction of the semiconductor multilayer stack and a size
in a slow axis direction that is perpendicular to the layer
stacking direction, and the plurality of auxiliary semiconductor
laser devices are arranged along a second same line extending in
the fast axis direction, the second same line being parallel to the
same line.
13. The line beam irradiation apparatus of claim 1, wherein each of
the plurality of semiconductor laser devices is stored in a package
or cartridge, and the support includes a connector for detachably
holding the package or cartridge.
14. A line beam source comprising: a plurality of semiconductor
laser devices; and a support for supporting the plurality of
semiconductor laser devices, wherein each of the plurality of
semiconductor laser devices includes a semiconductor multilayer
stack which has a facet, the facet including an emission region
from which laser light is to be emitted, the emission region having
a size in a fast axis direction that is parallel to a layer
stacking direction of the semiconductor multilayer stack and a size
in a slow axis direction that is perpendicular to the layer
stacking direction, and the plurality of semiconductor laser
devices are arranged along a same line extending in the fast axis
direction, and the laser light emitted from the emission regions of
respective ones of the plurality of semiconductor laser devices
diverge parallel to the same line to form a line beam.
15. A laser lift-off method with the use of the line beam
irradiation apparatus as set forth in claim 1, the method
comprising: providing a work which includes a carrier and a device
bound to the carrier and placing the work on the work stage;
irradiating the work placed on the work stage from the carrier side
with the line beam from the line beam source; and moving at least
one of the work stage and the line beam source such that an
irradiation position of the line beam on the work moves in a
direction transverse to the line beam.
16. An electronic device production method with the use of the line
beam irradiation apparatus as set forth in claim 1, the method
comprising: providing a work which includes a carrier and an
electronic device bound to the carrier and placing the work on the
work stage; irradiating the work placed on the work stage from the
carrier side with the line beam from the line beam source; moving
at least one of the work stage and the line beam source such that
an irradiation position of the line beam on the work moves in a
direction transverse to the line beam; and obtaining the electronic
device delaminated from the carrier of the work.
Description
TECHNICAL FIELD
[0001] The present application relates to a line beam source and a
line beam irradiation apparatus. The present application also
relates to a laser lift-off method and an electronic device
production method which are carried out using the line beam
irradiation apparatus.
BACKGROUND ART
[0002] In the technical field of production of electronic devices
such as high-luminance LED (Light Emitting Diode) and flexible
display, development of the laser lift-off method has been
intensively advanced. In the case where a high-luminance LED is
produced using a laser lift-off method, firstly, an LED including a
multilayer stack of a nitride semiconductor is formed on a
crystal-growth substrate, such as sapphire substrate. Thereafter,
the LED is separated from the crystal-growth substrate by the laser
lift-off method. In the case where a flexible display is produced,
a polymer layer is formed on a glass substrate which serves as a
carrier, and thereafter, a device is formed on the polymer layer,
which includes a thin film transistor layer and an organic light
emitting diode (OLED) layer. After completion of the formation
process, the device is delaminated together with the polymer layer
from the glass substrate by the laser lift-off method.
[0003] According to the laser lift-off method, it is necessary to
irradiate the carrier (work) to which the device is bound with a
laser beam of high light intensity such that a delamination
phenomenon is caused by a thermal or photochemical reaction.
Nowadays, as the source of the laser beam, a high power excimer
laser equipment is usually used. A pulsed laser light emitted from
the excimer laser equipment is shaped into a light beam whose
cross-sectional shape is like an elongated line. Such a linear
light beam is referred to as "line beam". The cross-sectional shape
of the line beam on the work, i.e., the shape of a region
irradiated with the light, is a rectangle of, for example, 720 mm
in the long axis direction and 1 mm in the short axis
direction.
[0004] An excimer laser annealing (ELA) unit which includes a
complicated optical system for formation of a line beam has been
put into practice as a unit for melting and recrystallizing a
non-crystalline silicon film in a flat panel display production
process. The ELA unit used for melting and recrystallizing a
non-crystalline silicon film has been diverted to the laser
lift-off method. The ELA unit is bulky, complicated in operation,
and highly expensive in price and running cost.
[0005] Semiconductor laser devices, which are less expensive and
easier in operation than the ELA unit, have had increasing laser
power. Thus, replacing part of the ELA unit with high-power
semiconductor laser devices has been studied. For example, a module
of a laser diode array has been developed in which laser bars each
including a plurality of emission regions (emitters) aligned in the
horizontal direction are vertically stacked up. Such a laser diode
array includes a large number of emitters two-dimensionally arrayed
at high density and can therefore achieve a high optical output
exceeding 1 kilowatt (kW) in total.
[0006] Patent Documents Nos. 1 and 2 disclose a two-dimensional
planar array (laser diode array) of a plurality of semiconductor
laser devices.
[0007] Patent Document No. 3 discloses a laser processing apparatus
including a plurality of blue semiconductor laser devices each of
which has an average power of not less than 1 watt. In this laser
processing apparatus, laser light emitted from respective ones of
the blue semiconductor laser devices are combined using optical
fibers, whereby high-power laser light is generated.
CITATION LIST
Patent Literature
[0008] Patent Document No. 1: Japanese Laid-Open Patent Publication
No. 2009-170881 [0009] Patent Document No. 2: U.S. Pat. No.
6,240,116 [0010] Patent Document No. 3: Japanese Laid-Open Patent
Publication No. 2013-233556
SUMMARY OF INVENTION
Technical Problem
[0011] In the laser diode arrays disclosed in Patent Documents Nos.
1 and 2, laser light emitted from each emitter is collimated by a
collimation lens into a parallel light beam. A bunch of the light
beams is shaped by an optical system which includes reflection
mirrors and other lenses so as to have a desired cross-sectional
shape. When such an existing high-power laser diode array is used
in laser lift-off, it is necessary to shape light beams emitted
from a planar array light source into a desired line beam.
[0012] In the laser processing apparatus disclosed in Patent
Document No. 3, each of a plurality of semiconductor laser devices
is connected with an optical fiber, and therefore, high-precision
alignment is required. In introduction of laser light into an
optical fiber and during the process of transmitting laser light
through the optical fiber, optical losses occur. Further, since the
cross section of the laser light coming out of the optical fiber is
circular, an optical system for shaping the laser light into a line
beam is indispensable, and a further loss occurs in the beam
shaping.
[0013] In a laser lift-off method for production of a small-sized
flexible display, using a YAG laser (yttrium aluminum garnet
solid-state laser) device, which is relatively inexpensive as
compared with the ELA unit, has been studied. However, the YAG
laser device also has the same problems as those of the ELA
unit.
[0014] According to an embodiment of the present disclosure, a
novel line beam source and a novel line beam irradiation apparatus
which can be suitably used in the laser lift-off method are
provided.
Solution to Problem
[0015] An exemplary embodiment of the line beam irradiation
apparatus of the present invention includes: a work stage; a line
beam source for irradiating a work placed on the work stage with a
line beam; and a transporting device for moving at least one of the
work stage and the line beam source such that an irradiation
position of the line beam on the work moves in a direction
transverse to the line beam. The line beam source includes a
plurality of semiconductor laser devices and a support for
supporting the plurality of semiconductor laser devices. Each of
the plurality of semiconductor laser devices includes a
semiconductor multilayer stack which has a facet, the facet
including an emission region from which laser light is to be
emitted. The emission region has a size in a fast axis direction
that is parallel to a layer stacking direction of the semiconductor
multilayer stack and a size in a slow axis direction that is
perpendicular to the layer stacking direction. The plurality of
semiconductor laser devices are arranged along a same line
extending in the fast axis direction, and the laser light emitted
from the emission regions of respective ones of the plurality of
semiconductor laser devices diverge parallel to the same line to
form the line beam.
[0016] An embodiment of the line beam source of the present
invention includes: a plurality of semiconductor laser devices; and
a support for supporting the plurality of semiconductor laser
devices. Each of the plurality of semiconductor laser devices
includes a semiconductor multilayer stack which has a facet, the
facet including an emission region from which laser light is to be
emitted. The emission region has a size in a fast axis direction
that is parallel to a layer stacking direction of the semiconductor
multilayer stack and a size in a slow axis direction that is
perpendicular to the layer stacking direction. The plurality of
semiconductor laser devices are arranged along a same line
extending in the fast axis direction, and the laser light emitted
from the emission regions of respective ones of the plurality of
semiconductor laser devices diverge parallel to the same line to
form a line beam.
[0017] A laser lift-off method of the present invention is a laser
lift-off method with the use of the line beam irradiation apparatus
as set forth in any of the foregoing paragraphs, the method
including: providing a work which includes a carrier and a device
bound to the carrier and placing the work on the work stage;
irradiating the work placed on the work stage from the carrier side
with the line beam from the line beam source; and moving at least
one of the work stage and the line beam source such that an
irradiation position of the line beam on the work moves in a
direction transverse to the line beam.
[0018] An electronic device production method of the present
invention is an electronic device production method with the use of
the line beam irradiation apparatus as set forth in any of the
foregoing paragraphs, the method including: providing a work which
includes a carrier and an electronic device bound to the carrier
and placing the work on the work stage; irradiating the work placed
on the work stage from the carrier side with the line beam from the
line beam source; moving at least one of the work stage and the
line beam source such that an irradiation position of the line beam
on the work moves in a direction transverse to the line beam; and
obtaining the electronic device delaminated from the carrier of the
work.
Advantageous Effects of Invention
[0019] According to an embodiment of the present invention, a line
beam source which can replace the ELA unit is provided in order to
form a line beam by taking advantage of such a characteristic that
laser light emitted from a semiconductor laser device diverges
anisotropically due to a diffraction effect.
BRIEF DESCRIPTION OF DRAWINGS
[0020] FIG. 1 is a perspective view schematically showing a basic
configuration of a typical semiconductor laser device.
[0021] FIG. 2A is a perspective view schematically showing the
spread (divergence) of laser light 30 coming out from an emission
region 24 of a semiconductor laser device 10.
[0022] FIG. 2B is a side view schematically showing the divergence
of the laser light 30. In the right part of FIG. 2B, a front view
of the semiconductor laser device 10 as viewed from the positive
direction of the Z-axis is also shown for reference.
[0023] FIG. 2C is a top view schematically showing the divergence
of the laser light 30.
[0024] FIG. 2D is a graph representing the divergence of the laser
light 30 in the Y-axis (fast axis) direction.
[0025] FIG. 2E is a graph representing the divergence of the laser
light 30 in the X-axis (slow axis) direction.
[0026] FIG. 3 is a graph representing an example of the
relationship between the size in the Y-axis direction, Fy, and the
size in the X-axis direction, Fx, of a cross section of the laser
light 30 and the distance from the emission region 24 (the position
in the Z-axis direction).
[0027] FIG. 4A is a front view showing a configuration example of a
laser diode array as viewed from the positive direction of the
Z-axis.
[0028] FIG. 4B is a diagram schematically illustrating the effect
of fast axis collimation lenses 50F.
[0029] FIG. 5 is a perspective view showing a configuration example
of a line beam source 100 in an embodiment of the present
invention.
[0030] FIG. 6 is a perspective view showing a configuration example
of a semiconductor laser device 40 in an embodiment of the present
invention.
[0031] FIG. 7A is a front view of the four semiconductor laser
devices 40 shown in FIG. 5 as viewed from the positive direction of
the Z-axis.
[0032] FIG. 7B is a front view of line beams 30L from the
semiconductor laser devices 40 as viewed from the positive
direction of the Z-axis.
[0033] FIG. 7C is a side view showing that the laser light 30
emitted from the semiconductor laser devices 40 form a line beam
30L.
[0034] FIG. 8A is a graph schematically representing an example of
the light intensity distribution in the fast axis direction of the
line beam 30L formed by merging together the laser light emitted
from the four semiconductor laser devices 40.
[0035] FIG. 8B is a graph schematically representing an example of
the light intensity distribution in the fast axis direction of the
laser light emitted from the four semiconductor laser devices
40.
[0036] FIG. 9A is a diagram showing a configuration example which
converges the line beam 30L in the slow axis direction, rather than
the fast axis direction, using a cylindrical lens 50S.
[0037] FIG. 9B is a diagram schematically showing a cross section
of the line beam 30L with the width (the size in the slow axis
direction) shortened by the cylindrical lens 50S.
[0038] FIG. 10 is a perspective view schematically showing a
configuration example of a line beam irradiation apparatus 1000 of
the present embodiment.
[0039] FIG. 11 is a block diagram schematically showing the flow of
signals, data, and instructions in the line beam irradiation
apparatus 1000.
[0040] FIG. 12 (each of the upper and lower parts of FIG. 12) is a
diagram of the line beam irradiation apparatus 1000 shown in FIG.
10 as viewed from a direction perpendicular to the YZ plane.
[0041] FIG. 13 is a diagram of the line beam irradiation apparatus
1000 as viewed from a direction perpendicular to the XZ plane in
the step of scanning a work 300 with a line beam (at three phases
(start, middle and end) of the step).
[0042] FIG. 14 is a graph representing an example of the
relationship between the irradiation position of the line beam 30L
and the optical output waveform.
[0043] FIG. 15 is a graph representing another example of the
relationship between the irradiation position of the line beam 30L
and the optical output waveform.
[0044] FIG. 16 is a graph representing still another example of the
relationship between the irradiation position of the line beam 30L
and the optical output waveform.
[0045] FIG. 17 is a graph representing still another example of the
relationship between the irradiation position of the line beam 30L
and the optical output waveform.
[0046] FIG. 18A is a cross-sectional view of a step for
illustrating an embodiment of laser lift-off.
[0047] FIG. 18B is a cross-sectional view of a step for
illustrating an embodiment of laser lift-off.
[0048] FIG. 18C is a cross-sectional view of a step for
illustrating an embodiment of laser lift-off.
[0049] FIG. 19 is a plan view schematically showing a region on the
work 300 irradiated with the line beam 30L.
[0050] FIG. 20 is a schematic cross-sectional view showing an
example where the light intensity distribution of the line beam 30L
is spatially modulated according to the position of the work
300.
[0051] FIG. 21A shows two columns of semiconductor laser devices 40
which are separated by the distance between the centers, Px.
[0052] FIG. 21B is a perspective view showing a configuration
example of the line beam source 100 which realizes the arrangement
of FIG. 21A.
[0053] FIG. 21C schematically shows the positions of the emission
regions 24 in the two columns of semiconductor laser devices 40,
which are projected onto the work 300.
[0054] FIG. 21D is a perspective view showing another configuration
example of the line beam source 100 which realizes the arrangement
of FIG. 21A.
[0055] FIG. 21E is a perspective view showing a configuration
example of the line beam source 100 which realizes a variation of
the arrangement of FIG. 21A.
[0056] FIG. 22A is a plan view showing semiconductor laser devices
40 in a staggered arrangement.
[0057] FIG. 22B is a perspective view showing a configuration
example of the line beam source 100 which realizes the staggered
arrangement of FIG. 22A.
[0058] FIG. 22C is a plan view schematically showing the positions
of the emission regions 24 of the semiconductor laser devices 40 in
the staggered arrangement, which are projected onto the work
300.
[0059] FIG. 23 is a plan view schematically showing the positions
of the emission regions 24 of semiconductor laser devices 40, which
are projected onto the work 300, where the distance between the
centers of adjoining semiconductor laser devices 40 varies
according to the position.
[0060] FIG. 24 is a diagram schematically showing the light
intensity distribution of a line beam 30L formed by semiconductor
laser devices 40 where the distance between the centers of
adjoining semiconductor laser devices 40 varies according to the
position.
[0061] FIG. 25 is a perspective view showing a configuration
example where the distance between the centers of adjoining
semiconductor laser devices varies according to the position.
DESCRIPTION OF EMBODIMENTS
[0062] The present inventor recognized that the light intensity
distribution of a line beam which is necessary for laser lift-off
does not need to have high uniformity unlike the line beam of the
ELA unit used for melting and recrystallization of a
non-crystalline silicon film, and then conceived the present
invention. A line beam source and a line beam irradiation apparatus
of the present disclosure form a line beam by taking advantage of
such a characteristic that laser light emitted from a semiconductor
laser device diverges anisotropically due to a diffraction effect.
Firstly, this diffraction effect is described.
[0063] <Diffraction Effect of Semiconductor Laser Device>
[0064] FIG. 1 is a perspective view schematically showing a basic
configuration of a typical semiconductor laser device. In the
drawing, the coordinate axes including the X-axis, the Y-axis and
the Z-axis which are perpendicular to one another are shown. Also
in the other attached drawings, the coordinate axes are shown. The
X-axis, the Y-axis and the Z-axis represent common directions among
all the drawings.
[0065] The semiconductor laser device 10 shown in FIG. 1 includes a
semiconductor multilayer stack 22 which has an end face (a facet)
26a. The facet 26a includes an emission region (emitter) 24 from
which laser light is to be emitted. In this example, the
semiconductor multilayer stack 22 is supported on a semiconductor
substrate 20 and includes a p-side cladding layer 22a, an active
layer 22b, and an n-side cladding layer 22c. On the upper surface
26b of the semiconductor multilayer stack 22, a p-side electrode 12
in the shape of a stripe is provided. On the rear surface of the
semiconductor substrate 20, an n-side electrode 16 is provided.
When an electric current which is greater than a threshold flows
through a predetermined region of the active layer 22b from the
p-side electrode 12 to the n-side electrode 16, laser oscillation
occurs. The facet 26a of the semiconductor multilayer stack 22 is
covered with an unshown reflective film. Laser light is emitted
from the emission region 24 via the reflective film.
[0066] The configuration shown in FIG. 1 is merely an example of
the configuration of the semiconductor laser device 10 and is
simplified for the sake of simple description. This simplified
configuration example does not limit embodiments of the present
disclosure which will be described later. Note that, in the other
drawings, constituents such as the n-side electrode 16 will be
omitted for simplicity.
[0067] In the semiconductor laser device 10 shown in FIG. 1, the
facet 26a of the semiconductor multilayer stack 22 is parallel to
the XY plane, and therefore, laser light is emitted in the Z-axis
direction from the emission region 24. The optical axis of the
laser light is parallel to the Z-axis direction. The emission
region 24 in the facet 26a has a size Ey in a direction parallel to
the stacking direction of the semiconductor multilayer stack 22
(Y-axis direction) and a size Ex in a direction perpendicular to
the stacking direction (X-axis direction). In general, the
relationship of Ey<Ex holds.
[0068] The size in the Y-axis direction of the emission region 24,
Ey, is defined by the thickness of the active layer 22b. The
thickness of the active layer 22b is usually equal to or smaller
than about half the laser oscillation wavelength. Meanwhile, the
size in the X-axis direction of the emission region 24, Ex, can be
defined by a structure which confines in a horizontal transverse
direction (X-axis direction) an electric current or light which
contributes to laser oscillation. In the example of FIG. 1, the
size Ex can be defined by the width of the p-side electrode 12 in
the shape of a stripe. In general, the size in the Y-axis direction
of the emission region 24, Ey, is equal to or smaller than about
0.1 .mu.m, and the size in the X-axis direction, Ex, is greater
than 1 .mu.m. To increase the optical output, increasing the size
in the X-axis direction of the emission region 24, Ex, is
effective. The size in the X-axis direction, Ex, can be set to, for
example, 50 .mu.m or more.
[0069] In this specification, Ex/Ey is referred to as the "aspect
ratio" of the emission region. The aspect ratio (Ex/Ey) in the
high-power semiconductor laser device can be set to, for example,
50 or more or may be set to 100 or more. In this specification, a
semiconductor laser device whose aspect ratio (Ex/Ey) is not less
than 50 is referred to as "broad area type semiconductor laser
device". In many cases, the broad area type semiconductor laser
device oscillates such that the horizontal transverse mode is
multiple modes rather than a single mode.
[0070] FIG. 2A is a perspective view schematically showing the
spread (divergence) of laser light 30 coming out from the emission
region 24 of the semiconductor laser device 10. FIG. 2B is a side
view schematically showing the divergence of the laser light 30.
FIG. 2C is a top view schematically showing the divergence of the
laser light 30. In the right part of FIG. 2B, a front view of the
semiconductor laser device 10 as viewed from the positive direction
of the Z-axis is also shown for reference.
[0071] The size in the Y-axis direction of a cross section of the
laser light 30 is defined by length Fy, and the size in the X-axis
direction of the cross section is defined by length Fx. Fy is the
FWHM (Full Width at Half Maximum) in the Y-axis direction relative
to the light intensity of the laser light 30 on the optical axis in
a plane intersecting with the optical axis of the laser light 30.
Likewise, Fx is the FWHM in the X-axis direction relative to the
light intensity of the laser light 30 on the optical axis in the
above-described plane.
[0072] The divergence of the laser light 30 in the Y-axis direction
is defined by angle .theta.f. The divergence of the laser light 30
in the X-axis direction is defined by angle .theta.s. .theta.f is
the full angle at half maximum in the YZ plane relative to the
light intensity of the laser light 30 at the intersection of a
spherical surface equidistant from the center of the emission
region 24 with the optical axis of the laser light 30. Likewise,
.theta.s is the full angle at half maximum in the XZ plane relative
to the light intensity of the laser light 30 at the intersection of
a spherical surface equidistant from the center of the emission
region 24 with the optical axis of the laser light 30.
[0073] FIG. 2D is a graph representing an example of the divergence
of the laser light 30 in the Y-axis direction. FIG. 2E is a graph
representing an example of the divergence of the laser light 30 in
the X-axis direction. In the graphs, the vertical axis represents
the normalized light intensity, and the horizontal axis represents
the angle. The light intensity of the laser light 30 exhibits a
peak value on the optical axis which is parallel to the Z-axis. As
seen from FIG. 2D, the light intensity in a plane which includes
the optical axis of the laser light 30 and which is parallel to the
YZ plane generally exhibits a Gaussian distribution. Meanwhile, the
light intensity in a plane which includes the optical axis of the
laser light 30 and which is parallel to the XZ plane exhibits a
narrow distribution which has a relatively flat top as shown in
FIG. 2E. In many cases, this distribution has a plurality of peaks
which are attributed to multimode oscillation.
[0074] Lengths Fy, Fx which define the cross-sectional size of the
laser light 30 and angles .theta.f, .theta.s which define the
divergence of the laser light 30 can be defined differently from
the above-described definitions.
[0075] As seen from the graphs, the divergence of the laser light
30 coming out from the emission region 24 is anisotropic. In
general, the relationship of .theta.f>.theta.s holds. The reason
why .theta.f is large is that the size in the Y-axis direction of
the emission region 24, Ey, is not more than the wavelength of the
laser light 30 and, therefore, strong diffraction occurs in the
Y-axis direction. Meanwhile, the size in the X-axis direction of
the emission region 24, Ex, is sufficiently greater than the
wavelength of the laser light 30 so that diffraction is unlikely to
occur in the X-axis direction.
[0076] FIG. 3 is a graph representing an example of the
relationship between the size in the Y-axis direction, Fy, and the
size in the X-axis direction, Fx, of a cross section of the laser
light 30 and the distance from the emission region 24 (the position
in the Z-axis direction). As seen from FIG. 3, the cross section of
the laser light 30 exhibits a near field pattern (NFP) which is
relatively long in the X-axis direction in the vicinity of the
emission region 24 but exhibits a far field pattern (FFP) which is
elongated in the Y-axis direction at a position sufficiently
distant from the emission region 24.
[0077] That it, the divergence of the cross section of the laser
light 30 becomes "faster" in the Y-axis direction but "slower" in
the X-axis direction as the distance from the emission region 24
increases. Thus, where the semiconductor laser device 10 is at the
origin of the coordinate system, the Y-axis direction is referred
to as "fast axis" direction, and the X-axis direction is referred
to as "slow axis" direction.
[0078] In the laser diode arrays disclosed in Patent Documents Nos.
1 and 2, a collimation lens is provided near the emission region of
the semiconductor laser device or laser bar in order to suppress
the divergence of the light beam in the fast axis direction. Such a
collimation lens is referred to as "fast axis collimation
lens".
[0079] FIG. 4A is a front view showing a configuration example of a
laser diode array 400 as viewed from the positive direction of the
Z-axis. FIG. 4B is a diagram schematically illustrating the effect
of the fast axis collimation lenses.
[0080] The laser diode array 400 illustrated in FIG. 4A is a
vertical stack in which four laser bars 410 extending in the X-axis
direction are stacked up in the Y-axis direction. Each of the laser
bars 410 includes eight emission regions 24. In the illustrated
laser diode array, laser light which has high light intensity in
total is obtained from thirty-two emission regions 24 arranged in
four rows and eight columns in the same plane. These emission
regions 24 emit laser light concurrently based on an electric
current flowing from the p-side electrode 12 in the shape of a
stripe to an unshown n-side electrode.
[0081] In the example of FIG. 4B, the fast axis collimation lenses
50F are provided on the emission surface side of the laser bars
410. Each of the fast axis collimation lenses 50F typically has a
shape elongated in the X-axis direction and faces a plurality of
emission regions 24 of a corresponding one of the laser bars 410.
The laser light 30 entering the fast axis collimation lens 50F is
collimated into parallel laser light 30C. Laser light coming out
from a laser diode array in which a large number of radiants are
compactly arranged in a rectangular region and which is bright in
the shape of a plane is shaped using another optical system,
whereby the light can be converted to a light beam which has
various cross-sectional shapes. The pitch in the Y-axis direction
of the laser bars 410 is, for example, from about 2 mm to about 5
mm. By compactly arranging a large number of emission regions 24 in
a limited area, a planar laser light source of high luminance can
be realized.
[0082] A line beam can also be formed using the above-described
laser diode array. However, for shaping laser light emitted from a
planar light source into a line beam which has a desired
cross-sectional shape, a complicated optical system consisting of
other lenses or mirrors is necessary in addition to the fast axis
collimation lenses 50F. As a result, the apparatus becomes bulky,
and the problem of misalignment in the optical system or the like
arises.
[0083] The present inventor recognized a problem which arises in
forming a line beam using a beam shaping technique after the "fast
axis collimation" such as illustrated in FIG. 4B and carried out
various examinations in order to find a solution to the problem. As
a result, the present inventor found that a practical line beam can
be formed by positively utilizing such a characteristic that light
emitted from a semiconductor laser device spreads in the fast axis
direction due to a diffraction effect, instead of the "fast axis
collimation". The present inventor also found that modulation of
the spatial intensity distribution can be added to scanning of the
line beam by using the emission region of a semiconductor laser
device as a component which is capable of adjusting the light
intensity independently of the other semiconductor laser devices,
rather than merely a part of a uniformly-emitting planar light
source. It was also found that, particularly for laser lift-off
purposes, high light intensity uniformity is not necessary unlike a
line beam for melting and recrystallization of a non-crystalline
silicon film. Rather, it was also found that it is desirable to
spatially adjust the light intensity according to the structure of
an object which is to be delaminated.
Embodiments
[0084] Hereinafter, embodiments of a line beam source and a line
beam irradiation apparatus of the present disclosure and an
embodiment of a laser lift-off method are described with reference
to the drawings. Excessively detailed descriptions will sometimes
be omitted. For example, detailed description of a well-known
matter and repetitive descriptions of substantially identical
components will sometimes be omitted. This is for the sake of
precluding the following descriptions from being unnecessarily
redundant and assisting one skilled in the art to easily understand
the descriptions. The present inventor provides the attached
drawings and the following descriptions for the purpose of
assisting one skilled in the art to sufficiently understand the
present disclosure. The present inventor does not intend that these
drawings and descriptions limit the subject matter recited in the
claims.
[0085] <Line Beam Source>
[0086] An embodiment of the line beam source of the present
disclosure is not intended to function as a planar light source in
which a large number of emission regions are compactly arranged at
high density. Thus, a complicated optical system for shaping a
light beam emitted from such a planar light source into a line beam
is not necessary. The line beam source of the present disclosure is
capable of forming a line beam elongated in the fast axis direction
by effectively utilizing a characteristic of the semiconductor
laser device, i.e., such a characteristic that a diffraction effect
causes light beam to spread in the fast axis direction.
[0087] First, refer to FIG. 5 and FIG. 6. A nonlimiting exemplary
embodiment of the line beam source of the present invention
includes a plurality of semiconductor laser devices and a plurality
of supports 60a supporting the semiconductor laser devices 40 as
shown in FIG. 5. The plurality of semiconductor laser devices 40
are arranged along the same line extending in the fast axis
direction (Y-axis direction). Laser light emitted from the emission
regions 24 of respective ones of the semiconductor laser devices 40
diverge in parallel to the same line so as to form a line beam.
[0088] In the illustrated example, the number of semiconductor
laser devices 40 is four. The number of semiconductor laser devices
40 is not limited to this example but may be three or may be not
less than five. To form a long line beam for irradiating a
large-area region, more than 100 semiconductor laser devices 40 can
be arranged on the same line. In the case where a large glass
substrate of, for example, about 300 cm on each side is irradiated
through one scanning cycle, the length of the line beam needs to be
set to about 300 cm. In this case, when the arrangement pitch is
set to 20 mm (=2 cm), about 150 semiconductor laser devices 40 are
arranged on the same line.
[0089] Each of the semiconductor laser devices 40 can have the same
configuration as that of the semiconductor laser device 10 of FIG.
1 as shown in FIG. 6. Each of the plurality of semiconductor laser
devices 40 includes a semiconductor multilayer stack 22 which has a
facet 26a. The facet 26a includes an emission region 24 from which
laser light is to be emitted. The emission region 24 of the
semiconductor laser device 40 has a size Ey in the fast axis
direction (Y-axis direction) that is parallel to the layer stacking
direction of the semiconductor multilayer stack 22 and a size Ex in
the slow axis direction (X-axis direction) that is perpendicular to
the layer stacking direction. The aspect ratio (Ex/Ey) is not less
than 50. In the semiconductor laser device 10 of FIG. 1 and the
semiconductor laser device 40 of FIG. 6, corresponding components
are designated with identical reference numerals. Herein, in
principle, the description of common components will not be
repeated.
[0090] The semiconductor laser device 40 can be made of various
semiconductor materials and can have various configurations and
sizes according to the oscillation wavelength and the optical
output. When the laser light is required to have a wavelength in
the ultraviolet region (e.g., 300-350 nm), the semiconductor
multilayer stack 22 of the semiconductor laser device 40 can be
suitably made of a nitride semiconductor, such as AlGaN-based
semiconductor or InAlGaN-based semiconductor. To define the size in
the slow axis direction of the emission region 24, Ex, a ridge
stripe may be provided in the p-side cladding layer 22a such that
light confinement in the horizontal transverse direction is
realized. The active layer 22b may include a single or a plurality
of quantum well structures. The semiconductor multilayer stack 22
may include other semiconductor layers, such as a light guiding
layer, a buffer layer, and a contact layer. When the substrate 20
is a sapphire substrate, the n-side electrode 16 is provided on a
side of the substrate 20 on which the p-side electrode 12 is
provided.
[0091] In the present embodiment, the size in the fast axis
direction of the emission region 24, Ex, can be set to, for
example, 10 nm to 200 nm, and the size in the slow axis direction
of the emission region 24, Ey, can be set to, for example, 50 .mu.m
to 300 .mu.m. Ey can exceed 100 times Ex. As a result, angle
.theta.f that defines the divergence of the laser light 30 in the
Y-axis direction is, for example, 40-60.degree., and angle .theta.s
that defines the divergence of the laser light 30 in the X-axis
direction is, for example, 5-15.degree.. The oscillation wavelength
of the semiconductor laser device 40 can be set within the range
of, for example, 350 nm to 450 nm. If a semiconductor laser device
which can realize stable laser oscillation in a shorter-wavelength
region, for example, in a deep ultraviolet region, is available,
beam laser whose wavelength is 200 nm to 350 nm can be formed.
Accordingly, the line beam source can replace the ELA unit in a
broad range of uses.
[0092] The supports 60a may be suitably made of a conductor of high
thermal conductivity, e.g., a metal such as copper or a ceramic
material such as aluminum nitride. The semiconductor laser devices
40 may be mounted to the supports 60a while the semiconductor laser
devices 40 are held on an unshown submount. In this example, all
the supports 60a are held in a casing 60. The casing 60 is closed
with, for example, an unshown light-transmitting cover, whereby the
inside of the casing 60 can be shielded from the atmosphere. The
inside of the casing 60 is filled with a gas which is inert with
the semiconductor laser devices 40. Each of the semiconductor laser
devices 40 is supplied with electric power via an unshown wire
(metal wire, metal ribbon, or the like). To suppress increase of
the temperature of the semiconductor laser devices 40 during
operation, a thermoelectric cooling device (not shown) such as
Peltier device may be provided near the semiconductor laser devices
40. The supports 60a may include an internal channel for water
cooling and fins for air cooling.
[0093] In each of the semiconductor laser devices 40, an unshown
photodiode is provided near a facet 26c of the semiconductor laser
device 40 which is opposite to the emission-side facet 26a.
Although this facet 26c is covered with a reflective film which has
a relatively-high reflectance, part of laser light oscillating
inside the semiconductor laser device 40 leaks out from the facet
26c. This laser light leakage is detected by the photodiode,
whereby the intensity of laser light emitted from the facet 26a can
be monitored. The output of the photodiode is sent to a driving
circuit for the semiconductor laser device 40, which will be
described later, and then used for power control.
[0094] FIG. 7A is a front view of the four semiconductor laser
devices 40 shown in FIG. 5 as viewed from the positive direction of
the Z-axis. The arrangement pitch of the semiconductor laser
devices 40 in the fast axis direction is Py. The arrangement pitch
is defined by the distance between the centers of the emission
regions 24. For simplicity, the supports 60a are not shown. FIG. 7B
is a front view of line beams 30L from the semiconductor laser
devices 40 as viewed from the positive direction of the Z-axis.
FIG. 7C is a side view showing that the laser light 30 emitted from
the semiconductor laser devices 40 form a line beam 30L.
[0095] As seen from FIG. 7C, by adjusting the arrangement pitch Py
of the semiconductor laser devices 40 in the fast axis (Y-axis)
direction and the distance Lz from the facet 26a to an irradiated
surface 45, the overlapping length Ly of the laser light 30 in the
line beam 30L on the irradiated surface 45 can be controlled.
[0096] FIG. 8A is a graph schematically representing an example of
the light intensity distribution at the irradiated surface 45 of
the line beam 30L formed by merging together the laser light
emitted from the four semiconductor laser devices 40. The laser
light 30 emitted from each of the semiconductor laser devices 40
approximately has a Gaussian distribution along the fast axis
direction. As seen from FIG. 8A, adjoining laser light 30 overlap
each another such that a resultant single line beam 30L has uniform
light intensity. The peak positions of the laser light 30 occur at
intervals of the arrangement pitch Py of the semiconductor laser
devices 40. The peak positions of the laser light 30 do not depend
on the distance Lz from the facet 26a of the semiconductor laser
devices 40 to the irradiated surface 45, but the shape of the light
intensity distribution varies depending on the distance Lz.
[0097] When the distance Lz is constant and the arrangement pitch
Py is set to a sufficiently small value, laser light 30 emitted
from three or more semiconductor laser devices 40 adjoining one
another on the same line can overlap one another on the irradiated
surface 45. As the arrangement pitch Py decreases, the light
intensity distribution in the Y-axis direction of the line beam 30L
becomes more uniform. In the case of forming a line beam which has
an equal size (length) in the long axis direction, a desired
irradiation density can be achieved even if the power of each of
the semiconductor laser devices is set to a value sufficiently
lower than the maximum power value because the number density of
semiconductor laser devices arranged along the same line increases
as the arrangement pitch Py decreases. This contributes to
extension of the life of the semiconductor laser devices.
[0098] FIG. 8B represents an example of the light intensity
distribution at the irradiated surface 45 when the distance Lz from
the facet 26a of the semiconductor laser devices 40 to the
irradiated surface 45 is set to an extremely small value. In this
example, at the irradiated surface 45, laser light 30 emitted from
respective ones of the semiconductor laser devices 40 do not
substantially overlap one another. In the intensity distribution
shown in FIG. 8B, it is not recognized that a continuous "line
beam" is formed. In a preferred embodiment, the line beam exhibits
such a light intensity distribution that the minimum values
occurring between the peaks of the light intensity are not less
than half the peak intensity. Such a light intensity distribution
is realized when the size Fy, which is defined by the FWHM of the
laser light 30 emitted from each of the semiconductor laser devices
40, is not less than the arrangement pitch Py.
[0099] To increase the irradiation density (fluence; the unit is
joule/cm.sup.2) of the line beam 30L, it is preferred to decrease
the arrangement pitch Py such that the number density of the
semiconductor laser devices 40 is increased. However, in the
present disclosure, rather than the effect achieved by decreasing
the arrangement pitch Py, it is considered that the laser light 30
itself, which is emitted from each of the semiconductor laser
devices 40, can work as a "line beam", and the properties of the
laser light 30 are utilized. To this end, in a preferred embodiment
of the present disclosure, the arrangement pitch Py is set to a
large value as compared with the stack arrangement pitch in the
conventional laser diode array previously described with reference
to FIG. 4A and FIG. 4B. Specifically, the arrangement pitch Py is
set to 20 mm or more. In one form, Py is set to 30 mm or more. In
some uses, Py is set to 40 mm or more. The distance Lz from the
facet 26a of the semiconductor laser device 40 to the irradiated
surface 45 is set such that the laser light 30 overlap one another
at the irradiated surface 45 to form a line beam 30L. By thus
setting the arrangement pitch Py so as to be greater than in the
conventional laser diode array, the following effects are
obtained.
[0100] (1) A line beam 30L which has a given length can be formed
by a smaller number of semiconductor laser devices 40. Furthermore,
a line beam which has a light intensity distribution required for
laser lift-off is sufficiently obtained.
[0101] (2) As the interval between adjoining semiconductor laser
devices 40 increases, heat produced in each of the semiconductor
laser devices 40 is more likely to dissipate to the outside. A
configuration where a heat sink which is made of a material of high
thermal conductivity is in contact with both the upper and lower
surfaces of each of the semiconductor laser devices 40 can be
readily employed.
[0102] (3) A dimensional clearance is secured for allowing the
semiconductor laser devices 40 mounted to a package or cartridge to
be placed on the supports 60a instead of placing the semiconductor
laser devices 40 in the form of chips on the supports 60a.
According to a configuration where the semiconductor laser devices
40 are detachably supported by the supports 60a, when one of the
plurality of semiconductor laser devices 40 has a breakdown, the
broken semiconductor laser device 40 can be selectively replaced by
an operable semiconductor laser device.
[0103] FIG. 9A is a diagram showing a configuration example which
converges the line beam 30L in the slow axis direction, rather than
the fast axis direction, using a cylindrical lens 50S. FIG. 9B is a
diagram schematically showing a cross section of the line beam 30L
with the width (the size in the X-axis direction) shortened by the
cylindrical lens 50S. The line beam source of the present
disclosure does not collimate or converge laser light in the fast
axis direction but does not exclude such shaping of the laser light
in the slow axis direction. When the size in the slow axis
direction (width) of the line beam 30L is shortened by a lens or
the like, the irradiation density (fluence) at the irradiated
surface can be improved.
[0104] In order to adjust the intensity distribution in the fast
axis direction of the line beam, an optical part whose light
transmittance, refractive index or optical thickness varies along
the fast axis direction may be added on the optical path of the
line beam 30L. Such an optical part does not substantially shorten
the length (the size in the fast axis direction) of the line beam
such that the irradiation density (fluence) is improved.
[0105] As described above, according to the line beam source of the
present disclosure, the anisotropic spread (divergence) of the
laser light exhibited by the semiconductor laser device can be
efficiently utilized. Thus, this line beam source does not provide
a planar light source which exhibits evened high luminance unlike
the conventional laser diode array.
[0106] <Line Beam Irradiation Apparatus>
[0107] See FIG. 10. FIG. 10 is a perspective view schematically
showing a configuration example of a line beam irradiation
apparatus 1000 of the present embodiment. The line beam irradiation
apparatus 1000 includes a work stage 200 and a line beam source
(laser head) 100 for irradiating a work 300 placed on the work
stage 200 with line beam 30L. Typical examples of the work 300
include a flexible display and a high-luminance LED under
manufacture, although the present invention is not limited to these
examples. Examples of the work 300 include a wide variety of
objects which can be physically or chemically changed by
irradiation with the line beam 30L. Such a physical or chemical
change can be utilized not only for delamination but also for
processing of an object, reforming, melting, crystallization,
recrystallization, cutting, activation of impurities in
semiconductor, and sterilization.
[0108] The line beam irradiation apparatus 1000 includes a
transporting device 250 for moving at least one of the work stage
200 and a line beam source 100 such that the irradiation position
30P of the line beam 30L on the work 300 moves in a direction
transverse to the line beam 30L. The transporting device 250
includes an actuator such as, for example, a motor M. The motor M
may be a rotating electric machine, such as DC motor, three-phase
AC motor, stepping motor, or may be a linear motor or an ultrasonic
motor. When an ultrasonic motor is used, highly-accurate
positioning is possible as compared with the other types of motors.
Further, the ultrasonic motor provides large holding power when it
is not moving, and can hold without supply of electric power.
Therefore, the heat generation is small when it is not moving.
Further, the ultrasonic motor is particularly advantageous when the
work is sensitive to magnetism because the ultrasonic motor does
not include a magnet.
[0109] The transporting device 250 is connected with a transporting
device driving circuit 90. The transporting device driving circuit
90 controls, for example, the rotation angle and the rotation speed
of the motor M in order to adjust the mutual positional
relationship between the line beam source 100 and the work stage
200. In an example described below, for simplicity, the line beam
source 100 moves in the direction of the rightward arrow of FIG. 10
while the work stage 200 is stationary. However, the line beam
irradiation apparatus 1000 of the present embodiment is not limited
to this example. The work stage 200 may move in the direction of
the leftward arrow of FIG. 10 while the line beam source 100 is
stationary. Alternatively, both the work stage 200 and the line
beam source 100 may move in an identical direction or in different
directions. When the work stage 200 moves while the work stage 200
supports a heavy-weight work 300, a bearing such as, for example,
air slider can be used.
[0110] As previously described with reference to FIG. 5, the line
beam source 100 includes a plurality of semiconductor laser devices
40 and supports 60a supporting the plurality of semiconductor laser
devices 40. The plurality of semiconductor laser devices 40 include
the above-described constituents and are arranged along the same
line extending in the fast axis direction. Laser light emitted from
the emission regions of respective ones of the plurality of
semiconductor laser devices 40 of the line beam source 100 diverge
in parallel to the same line so as to form a line beam 30L.
[0111] The distance (interval) from the lower edge of the line beam
source 100 to the upper surface of the work 300 can be set in the
range of, for example, about 5 mm to about 200 mm. Although the
upper surface of the work 300 shown in the drawing is flat, the
upper surface of the actual work 300 does not need to be flat. In
the example illustrated in FIG. 10, the line beam 30L is
perpendicularly incident on the upper surface of the work 300. In
other words, the optical axes of the laser light that are
constituents of the line beam 30L are parallel to the Z-axis while
the upper surface of the work stage 200 is parallel to the XY
plane. However, the embodiment of the line beam irradiation
apparatus of the present invention is not limited to such an
example. The upper surface of the work stage 200 may be inclined
with respect to the line beam 30L. The Z-axis does not need to be
identical with the vertical direction but may be inclined with
respect to (e.g., perpendicular to) the vertical direction.
[0112] To further even out the light intensity distribution
illustrated in FIG. 8A along the longitudinal direction (Y-axis
direction) of the line beam, the semiconductor laser devices 40 may
be oscillated or moved along the longitudinal direction (Y-axis
direction) of the line beam 30L during irradiation with the line
beam. Such oscillation or movement can also be realized by driving
the line beam source 100 itself using an unshown actuator.
Alternatively, it can also be realized by oscillating or moving
each of the semiconductor laser devices 40 in the fast axis
direction in the line beam source 100.
[0113] Each of the semiconductor laser devices 40 in the line beam
source 100 (see FIG. 5) is connected with a laser diode driving
circuit (LD driving circuit) 80. The LD driving circuit 80 may
include an automatic power control (APC) circuit which is
configured to receive an electric signal from the above-described
photodiode for monitoring and adjust the optical output of the
semiconductor laser devices 40 (see FIG. 5) to a predetermined
level. Alternatively, the LD driving circuit 80 may include an
automatic current control (ACC) circuit which is configured to
adjust the magnitude of an electric current (driving current)
flowing through the semiconductor laser devices 40 (see FIG. 5) to
a predetermined level. The LD driving circuit 80 can have a known
circuit configuration. When strict irradiation control over the
work is unnecessary, the photodiode for monitoring may be omitted
from the semiconductor laser devices. In this case, the
aforementioned ACC circuit is suitably used.
[0114] FIG. 11 is a block diagram schematically showing the flow of
signals, data, and instructions in the line beam irradiation
apparatus 1000.
[0115] In the configuration example shown in the drawing, a
controller 70 is typically a computer. A part or the entirety of
the controller 70 can be a general-purpose or special-purpose
computer system. The computer system includes an OS (operating
system) and, when necessary, hardware devices such as peripheral
devices. The controller 70 is connected with a memory 74 which is a
computer-readable storage medium. In the memory 74, a program is
stored which defines the operation of the line beam irradiation
apparatus 1000. In FIG. 11, for simplicity, a single memory unit is
shown. However, the actual memory 74 can consist of a plurality of
storage devices of the same type or different types. A part of the
memory 74 may be a nonvolatile memory while the other part may be a
random access memory. A part or the entirety of the memory 74 may
be an easily-detachable optical disc or solid-state storage device
or may be a cloud-type storage on a network.
[0116] The controller 70 is connected with a sensor 76, such as
temperature sensor and image sensor. Such a sensor 76 enables
detection of the irradiation position 30P of the line beam 30L on
the work 300 (FIG. 10) or monitoring of a physical or chemical
change in the work 300 which is caused by irradiation. When the
sensor 76 is an infrared image sensor, the sensor 76 also enables
detection of the temperature distribution over the work 300 heated
by irradiation with the line beam 30L. When the sensor 76 is a
visible-light image sensor, the sensor 76 also enables detection of
the in-plane distribution of a physical or chemical change in the
work 300 which is caused by irradiation with the line beam 30L.
Thus, when for example laser lift-off is carried out using the line
beam irradiation apparatus 1000 of the present embodiment, it is
also possible to detect whether or not delamination failure
occurred and the place of the delamination failure using the sensor
76. If the image sensor is configured to obtain three-dimensional
images, it is also possible to detect the three-dimensional
distribution of a physical or chemical change in the work 300 which
is caused by irradiation with the line beam 30L. Further, before
the irradiation, it is also possible to grasp the structure of the
work 300 and utilize the grasped structure in adjusting the
irradiation conditions.
[0117] The controller 70 follows the program stored in the memory
74 and issues appropriate instructions to the LD driving circuit 80
and the transporting device driving circuit 90, when necessary,
based on the output of the sensor 76. The LD driving circuit 80
adjusts the light intensity of the line beam 30L emitted from the
line beam source 100 according to the instruction from the
controller 70. The transporting device driving circuit 90 adjusts
the operation of the transporting device 250 according to the
instruction from the controller 70.
[0118] FIG. 12 is a diagram of the line beam irradiation apparatus
1000 shown in FIG. 10 as viewed from a direction perpendicular to
the YZ plane. The upper part of FIG. 12 shows the line beam
irradiation apparatus 1000 before the irradiation. The lower part
of FIG. 12 shows the line beam irradiation apparatus 1000 during
the irradiation. In this example, the length (the size in the long
axis direction) of the line beam 30L is greater than the length of
one side of the work 300. Therefore, line beam irradiation of the
entirety of the work 300 can be completed through one scanning
cycle. If the length of the line beam 30L is half the length of one
side of the work 300, two scanning cycles are necessary. In this
case, the scanning direction may be reversed between the forward
movement and the backward movement. In the line beam irradiation
apparatus 1000 of the present embodiment, the line beam 30L is not
enlarged or contracted in the long axis direction using an optical
element, such as beam expander or lens. Thus, the length of the
line beam 30L is generally equal to the total length of the array
of the semiconductor laser devices 40 in the line beam source 100
(FIG. 5). If the opposite end portions of the line beam 30L are
unnecessary for the irradiation, the opposite end portions of the
line beam 30L may be cut off by a blocking member inserted between
the line beam source 100 and the work 300.
[0119] FIG. 13 is a diagram of the line beam irradiation apparatus
1000 as viewed from a direction perpendicular to the XZ plane in
the step of scanning the work 300 with the line beam 30L (at three
phases (start, middle and end) of the step). In this example, the
scanning with the line beam 30L is realized by moving the line beam
source 100 in the X-axis direction while the work 300 is
stationary. As previously described, the scanning with the line
beam 30L can be realized by changing the relative positional
relationship between the line beam source 100 and the work stage
200.
[0120] The line beam 30L may be a continuous wave (CW) or may be a
pulsed wave. The LD driving circuit 80 of FIG. 11 is capable of
freely modulating emission of each of the semiconductor laser
devices 40. As shown in FIG. 13, the light intensity of the line
beam 30L can be temporally and spatially changed while the
irradiation position of the line beam 30L is moving.
[0121] FIG. 14 is a graph representing an example of the
relationship between the position of the line beam source 100 and
the light intensity variation (optical output waveform) of the line
beam 30L. In this graph, a line sloping upwards to the right
represents the relationship between the passage of time since the
start of the line beam irradiation step and the position of the
line beam source 100 (the position relative to the work). The
position of the line beam source 100 is represented by the x
coordinate for the sake of convenience. Above the graph, an example
of the optical output waveform of the line beam 30L is shown. In
the example of FIG. 14, the light intensity of the line beam 30L is
maintained constant after the line beam source 100 is lit up. The
position of the line beam source 100 moves at a constant scanning
speed. In this case, the "constant scanning speed" is not limited
to a constant speed by a continuous movement in a strict sense. For
example, it includes moving the line beam source 100 or the work
stage 200 in a step-by-step manner using a stepping motor, each
step being several tens of micrometers. Such a microscopic
step-by-step movement can be considered as being identical with a
substantially continuous movement.
[0122] Consider an example where the optical output of each of the
semiconductor laser devices 40 is 1 watt (W). Assume that the
irradiated region on the work 300 by a single semiconductor laser
device 40 has the size of 2.0 cm.times.0.5 cm. The area of the
irradiated region is 1 cm.sup.2. In this case, if the work 300 is
irradiated with laser light from a single semiconductor laser
device 40 for 1 second, the fluence is equal to 1 joule/cm.sup.2
(=1000 millijoule/cm.sup.2). Since the width of the line beam 30L
is 0.5 cm, if the scanning is carried out in a direction
perpendicular to the line beam 30L at the speed of 0.5 cm per
second, the work 300 is irradiated with laser light of 1000
millijoule/cm.sup.2. If the scanning is carried out in a direction
perpendicular to the line beam 30L at the speed of 2.0 cm per
second, the work 300 can be irradiated with laser light of 250
millijoule/cm.sup.2. Since laser light emitted from respective ones
of the semiconductor laser devices 40 partially overlap one
another, the fluence of the line beam 30L increases by the amount
of the overlaps. When the optical output of the semiconductor laser
devices 40 is increased, the scanning speed can be further
increased. In order to increase the optical output of the
semiconductor laser devices 40, increasing the size in the slow
axis direction of the emission region 24, Ex, is effective. Ex can
be set to, for example, 100 .mu.m or more, or 200 .mu.m or more. In
an embodiment of the laser lift-off method which will be described
later, delamination of a polyimide layer from a glass substrate
requires an irradiation density of about 250 millijoule/cm.sup.2 or
greater. Even when the optical output of the semiconductor laser
devices 40 is relatively low, a required irradiation density can be
achieved by increasing the irradiation duration. Alternatively, a
required irradiation intensity can also be achieved by making the
size in the short-axis direction (width) of the line beam smaller
than 0.5 cm. To this end, an optical system such as lens or mirror
may be coupled with each of the semiconductor laser devices 40. A
sufficient size in the short-axis direction of the line beam is
about 0.1 cm.
[0123] According to an embodiment of the line beam irradiation
apparatus of the present invention, the price of a single unit of
the apparatus can be decreased as compared with the ELA unit. Thus,
when a plurality of units of the line beam irradiation apparatus
are provided and each work is irradiated using each line beam
irradiation apparatus, it is not necessary to increase the scanning
speed to the limit level for the purpose of improving the mass
production efficiency. That is, according to an embodiment of the
line beam irradiation apparatus of the present invention, setting
the scanning speed of the line beam to a long value is economically
tolerated, and therefore, the life of the light source can be
extended by setting the optical output of each semiconductor laser
device to a low value.
[0124] FIG. 15 is a graph representing another example of the
relationship between the position of the line beam source 100 and
the optical output waveform. In the example of FIG. 15, after the
line beam source 100 is lit up, the light intensity of the line
beam oscillates with a constant short period. The position of the
line beam source 100 moves at a constant, relatively-low speed. In
this example, the line beam source 100 periodically alternates
between a lit-up state and a dark state. The ratio of the duration
of the lit-up state in one period is defined as the duty ratio. The
fluence can be adjusted using the duty ratio as a parameter. The
oscillation frequency (modulation frequency) of the light intensity
can be set in the range of, for example, 1 hertz (Hz) to several
kilohertz (kHz). The width of the line beam 30L (the size in the
X-direction at the irradiated surface), the modulation frequency,
and the scanning speed are set such that each region of the work
300 which is to be irradiated is subjected to the line beam
irradiation at least once.
[0125] FIG. 16 is a graph representing still another example of the
relationship between the position of the line beam source 100 and
the optical output waveform. In the example of FIG. 16, the duty
ratio is modulated during the scanning with the line beam 30L.
[0126] FIG. 17 is a graph representing still another example of the
relationship between the position of the line beam source 100 and
the optical output waveform. In the example of FIG. 17, the
scanning speed is not constant, and the position of the line beam
source 100 alternately moves and stops at constant time intervals.
In this example, the irradiation with the line beam 30L is carried
out while movement of the line beam source 100 relative to the work
stage 200 is stopped. During the irradiation with the line beam 30L
while the position in the X-axis direction of the line beam source
100 is stationary, the line beam 30L may be oscillated or moved in
the fast axis (Y-axis) direction as previously described.
Accordingly, at each region of the work 300, the distribution in
the fast axis (Y-axis) direction of the irradiation density is
evened out.
[0127] As described above, various modulations can be added to the
light intensity of the line beam 30L. It is also possible to change
the form of the modulation with time or according to the
irradiation position. The combination of the pattern of movement of
the irradiation position and the pattern of the light intensity
modulation is various and is not limited to the examples
illustrated in FIG. 14 to FIG. 17.
[0128] The distance between the line beam source 100 and the work
300 may be modulated although, in the above-described embodiments,
this distance is maintained constant during the scanning. In these
embodiments, laser light emitted from the semiconductor laser
devices 40 of the line beam source 100 impinges on the work 300
without being collimated or converged at least in the fast axis
direction. As previously described, a lens for converging the line
beam 30L in the slow axis direction may be added to the line beam
source 100. Further, for the purpose of adjusting the length of the
line beam 30L, an optical element, such as lens or mirror, may be
used to converge or expand the line beam 30L in the fast axis
direction.
[0129] <Laser Lift-Off Method>
[0130] FIG. 18A, FIG. 18B and FIG. 18C are cross-sectional views of
steps for illustrating an embodiment of the laser lift-off method
of the present invention. Each of these drawings is a
cross-sectional view enlargedly and schematically showing part of
the work 300. The dimensions of the work 300 shown in the drawings
do not reflect the scale ratio of the dimensions of the actual work
300.
[0131] As shown in FIG. 18A, the work 300 includes a glass
substrate (carrier) 32, a polyimide layer 34 bound to the glass
substrate 32, and a plurality of devices 36 formed on the polyimide
layer 34. In this example, respective ones of the plurality of
devices 36 have an identical structure. Each of the devices 36 has
a structure which operates as a flexible electronic device, e.g., a
flexible display, after the polyimide layer 34 is delaminated from
the glass substrate 32. A typical example of the devices 36 is an
electronic device which includes a thin film transistor layer, an
OLED layer, an electrode layer and a wire layer. The thin film
transistor can be made of amorphous silicon, polycrystalline
silicon, any other type of inorganic semiconductor layer, or an
organic semiconductor. Formation of the polycrystalline silicon can
be realized by melting and recrystallizing a non-crystalline
silicon layer deposited on the glass substrate 32 using a
conventional ELA unit. Each of the devices 36 is encapsulated with
a barrier film against moisture and gas.
[0132] FIG. 18B shows a state in the middle of irradiation of the
work 300 with the line beam 30L. In this example, the irradiation
with the line beam 30L causes formation of a gap 34a between the
glass substrate 32 and the polyimide layer 34. The wavelength of
the line beam 30L is selected such that large part of the line beam
30L is transmitted through the glass substrate 32 and absorbed by
the polyimide layer 34. When a polyimide layer 34 which has a
thickness of, for example, about 5-200 .mu.m is irradiated with a
line beam which has a wavelength of, for example, 250-450 nm (e.g.,
100-300 millijoule/cm.sup.2), the polyimide layer 34 can be
delaminated from the glass substrate 32. Of presently-existing
practical semiconductor laser devices, a semiconductor laser device
of the shortest wavelength has an oscillation wavelength of about
350 nm. It is expected that, in the future, this wavelength will be
further shortened and the optical output will be increased.
[0133] The spectral absorbance of polyimide and the spectral
transmittance of glass depend on the type of polyimide and the type
of glass, respectively. Thus, the material and thickness of these
constituents and the wavelength and light intensity of the line
beam 30L are determined such that the delamination efficiently
advances.
[0134] FIG. 18C shows a state after completion of the irradiation
of the work 300 with the line beam 30L. As illustrated in the
drawing, the plurality of devices 36 which are supported by the
polyimide layer 34 are lifted off and delaminated from the glass
substrate 32. When the plurality of devices 36 are supported by a
single continuous polyimide layer 34, the polyimide layer 34 is
divided after the laser lift-off process, and the plurality of
devices 36 are separated from one another. The thus-obtained
devices 36 do not include a highly-rigid constituent, such as the
glass substrate 32, and therefore have flexibility.
[0135] In the above-described example, in the work 300 used, the
polyimide layer 34 is in contact with the glass substrate 32.
However, application of the laser lift-off method of the present
invention is not limited to such an example. Between the glass
substrate 32 and the polyimide layer 34, a sacrificial layer may be
provided which absorbs laser light for enhancing delamination.
Alternatively, a layer which is made of a material other than
polyimide may be used as a base of a flexible device. Still
alternatively, a carrier which is made of a material other than
glass may be used instead of the glass substrate 32.
[0136] In the above-described example, a flexible display is
delaminated from a glass substrate. However, application of the
laser lift-off method of the present invention is not limited to
such an example. The laser lift-off method of the present invention
can also be used for deamination of an LED from a crystal-growth
substrate, such as sapphire substrate. According to an electronic
device production method including such a laser lift-off process, a
work which includes a carrier and various electronic devices bound
to the carrier is provided and then irradiated with a line beam,
whereby electronic devices delaminated from the carrier can be
obtained.
[0137] FIG. 19 is a plan view schematically showing a region on the
work 300 irradiated with the line beam 30L (a portion enclosed by a
broken line). Black dots in the irradiated region represent the
positions of the emission regions 24 of the semiconductor laser
devices 40 of the line beam source 100 (not shown), which are
projected onto the work 300. In this example, laser light emitted
from 12 semiconductor laser devices 40 form the line beam 30L.
[0138] As shown in FIG. 19, the structure of the work 300 is not
uniform according to the positions of projection of the emission
regions 24 of the 12 semiconductor laser devices 40. That is, the
work 300 includes a region in which the devices 36 are not present
and a region in which the devices 36 are present. Between these
regions, the heat capacity differs according to the
presence/absence of the devices 36. Thus, when these regions are
irradiated with laser light of the same light intensity, there is a
probability that the degree of delamination will differ between
these regions. The line beam irradiation apparatus 1000 is capable
of irradiating a portion of the work 300 which has a large heat
capacity with light of relatively-high light intensity and
irradiating a portion of the work 300 which has a small heat
capacity with light of relatively-low light intensity even if these
portions are on the same line.
[0139] FIG. 20 is a schematic cross-sectional view showing an
example where the light intensity distribution of the line beam 30L
is spatially modulated according to the position of the work 300.
Curves shown in the upper part of FIG. 20 represent the intensity
distribution of laser light emitted from the 12 semiconductor laser
devices 40. The broken line represents the light intensity
distribution of the merged line beam 30L. In this example, the 12
semiconductor laser devices 40 emit laser light of different powers
(light intensities) according to the position. The LD driving
circuit 80 of FIG. 10 and FIG. 11 is capable of independently
controlling the optical output of each of the semiconductor laser
devices 40.
[0140] As previously described with reference to FIG. 15 to FIG.
17, according to the present embodiment, temporal light intensity
modulation can be carried out. Further, spatial light intensity
modulation can also be carried out as illustrated in FIG. 20.
Changing the light intensity distribution of the line beam 30L
according to the irradiation position on the work 300 can be
realized by, generally, two methods described below.
[0141] The first method is to program in advance the light
intensity of a plurality of semiconductor laser devices according
to the structure of the work 300. The second method is to adjust or
correct the light intensity of a plurality of semiconductor laser
devices 40 in real time while monitoring the structure or state of
the work 300 using an image sensor. The latter method may be
combined into the former method. When the second method is carried
out, for example, the structure or state of the work 300 is
detected in real time using an image sensor, and an area which is
to be irradiated is divided into a plurality of cells by image
processing. The target value of the light intensity is set for each
cell, and the light intensity of each semiconductor laser device is
adjusted.
[0142] While scanning the work 300 with the line beam 30L, it is
also possible to detect a region in which delamination is
incomplete (delamination failure region) using, for example, an
image sensor. When such a delamination failure region is detected,
the positional coordinates of that region are stored in the memory
74. Then, the second scanning of that work 300 can be carried out.
The second scanning only requires irradiating only the delamination
failure region with laser light. In an extreme example, the second
scanning can be completed only by applying laser light from a
single semiconductor laser device 40 onto a single delamination
failure region.
[0143] The line beam irradiation apparatus 1000 may include two
line beam sources 100. When a delamination failure region caused
during the irradiation by the preceding first line beam source 100
is detected by an image sensor, one of the semiconductor laser
devices 40 of the succeeding second line beam source 100
corresponding to the detected delamination failure region is
selectively caused to emit light. By thus carrying out complemental
irradiation with laser light, repair of a defect can be realized in
the same step.
[0144] Alternatively, a single line beam source may include two
columns of semiconductor laser devices 40. FIG. 21A shows two
columns of semiconductor laser devices 40 which are separated by
the distance between the centers, Px. Px can be set in the range
of, for example, not less than 10 mm and not more than 200 mm. The
first column which is to irradiate earlier includes a plurality of
semiconductor laser devices 40 arranged at the pitch of Py1 in the
Y-axis direction. The succeeding column includes a plurality of
semiconductor laser devices 40 arranged at the pitch of Py2 in the
Y-axis direction. In the illustrated example, Py1=Py2, although the
present invention is not limited to this example. FIG. 21B is a
perspective view showing a configuration example of the line beam
source 100 which includes such semiconductor laser devices 40. FIG.
21C schematically shows the positions of the emission regions 24 in
the two columns of semiconductor laser devices 40, which are
projected onto the work 300. In the example of FIG. 21C, the work
300 is irradiated with the line beam 30L which is formed by a line
beam source in which each column includes 12 semiconductor laser
devices 40.
[0145] According to such an example, a region in which delamination
by irradiation with line beam 30L formed by a plurality of
semiconductor laser devices 40 included in the preceding first
column is not completed during scanning is adequately repaired by
lighting up one or more of a plurality of semiconductor laser
devices 40 included in the succeeding column. The semiconductor
laser devices 40 of the second column are arranged on the second
same line and serve as auxiliary semiconductor laser devices. As
shown in FIG. 21B, an image sensor 76a may be provided between the
first column and the second column of the semiconductor laser
devices 40 of the line beam source 100 for monitoring the state of
delamination. Furthermore, as shown in FIG. 21D, another image
sensor 76b may be provided behind the second column of the
semiconductor laser devices 40 as viewed in the scanning direction
for monitoring the state of delamination. When the moving direction
of the line beam source 100 is reversed such that the line beam
source 100 reciprocates, a still another image sensor 76c may be
further provided ahead of the first column of the semiconductor
laser devices 40 as shown in FIG. 21E. When the configuration of
FIG. 21E is employed, either one of the image sensors 76b, 76c is
always on the rear side as viewed in the scanning direction even if
the scanning direction is reversed, so that the state of
delamination can be monitored.
[0146] The two columns of the semiconductor laser devices 40 may be
close to each other by a distance of not more than 10 mm. The
process may be configured such that the semiconductor laser devices
40 of the preceding first column "preheat" a work, and the
semiconductor laser devices 40 of the succeeding second column
achieve "delamination". Various line beam irradiation processes can
be performed on the work 300 by allowing the semiconductor laser
devices 40 of the first column and the semiconductor laser devices
40 of the second column to produce line beams of different light
intensities. The number of columns is not limited to two. The laser
light emitted from the respective columns of the semiconductor
laser devices 40 have different wavelengths. The process may be
configured such that the preceding column emits a line beam of a
relatively-long wavelength, and then the succeeding column emits a
line beam of a relatively-short wavelength. Conversely, the process
may be configured such that the preceding column emits a line beam
of a relatively-short wavelength, and then the succeeding column
emits a line beam of a relatively-long wavelength.
[0147] FIG. 22A is a diagram showing another arrangement example of
the semiconductor laser devices 40 in the line beam source 100.
FIG. 22B is a perspective view showing a configuration example of
the line beam source 100 which includes the thus-arranged
semiconductor laser devices 40. FIG. 22C schematically shows the
positions of the emission regions 24 of the semiconductor laser
devices 40 arranged in two columns, which are projected onto the
work 300. In this example, the semiconductor laser devices 40
arranged in two columns have a stagger pattern (staggered
arrangement). By reducing the distance between the centers of the
two columns, a single line beam can be formed in total. When the
orientation of the semiconductor laser devices 40 is adjusted such
that the optical axes of the semiconductor laser devices 40
included in the first column and the optical axes of the
semiconductor laser devices 40 included in the second column
intersect with each other on the work 300, substantially a single
line beam can be formed. The light intensity of the thus-formed
line beam is more uniform in the fast axis direction.
[0148] FIG. 23 is a plan view schematically showing the positions
of the emission regions 24 of semiconductor laser devices 40, which
are projected onto the work 300, where the distance between the
centers of adjoining semiconductor laser devices 40 varies
according to the position. FIG. 24 is a diagram schematically
showing the light intensity distribution of the line beam 30L
formed by the thus-arranged semiconductor laser devices 40. FIG. 25
is a perspective view showing a configuration example of the line
beam source 100 which realizes the light intensity distribution
shown in FIG. 24. When the structure of the work 300 is already
known, the arrangement of the semiconductor laser devices 40 can be
adjusted in advance to the structure of the work 300. In a use
where a lift-off process is performed on a large quantity of works
300 which have the same structure, the arrangement of the
semiconductor laser devices 40 may be determined according to the
works 300.
[0149] As described in the foregoing, the embodiments of the line
beam source and the line beam irradiation apparatus of the present
invention can have various configurations according to the use or
the structure of a work.
[0150] In the above-described embodiments of the line beam source
and the line beam irradiation apparatus of the present invention, a
complicated optical system for making the light intensity or
fluence of a line beam constant along the longitudinal direction of
the line beam is unnecessary. Further, the price of the
semiconductor laser devices is extremely low as compared with the
price of excimer laser devices. Therefore, according to the
embodiments of the present invention, the cost of the line beam
irradiation apparatus and the laser lift-off method is decreased,
and a path for application of line beam irradiation to various uses
is made. The oscillation state of the semiconductor laser devices
can be easily turned on and off whereas the excimer laser devices
need to continue laser oscillation during the operation of the
apparatus. Thus, according to the embodiments of the present
invention, laser oscillation can be selectively carried out only in
part of the period of scanning of an irradiated region in which
light irradiation necessary for delamination is executed, so that
the life of the light source can be extended, and the running cost
such as electricity cost can be saved. Further, the line beam
irradiation apparatus of the present invention is capable of
emitting continuous wave laser light, rather than pulsed wave laser
light, and is therefore capable of emitting laser light of
relatively-low intensity for a relatively-long time as compared
with laser light irradiation by a conventional ELA unit and YAG
laser device. As a result, even if the uniformity in irradiation
density is low, the heat distribution in the work can be easily
evened out. The line beam irradiation apparatus of the present
invention can also be used instead of a conventional expensive ELA
unit and YAG laser device for melting and recrystallization of a
semiconductor layer. The variations of the line beam source 100
which have previously been described with reference to FIG. 21A to
FIG. 25 are also applicable to uses other than the laser lift-off
method.
[0151] In the attached drawings, for simplicity, the semiconductor
laser devices shown are in the form of bare chips. As previously
described, the semiconductor laser devices mounted to a package or
cartridge may be placed on the supports 60a. In that case, the
supports have a connector for holding the package or cartridge.
Such a connector can have an arbitrary structure so long as it has
a mechanism for detachably holding each package or cartridge.
[0152] Each of the semiconductor laser devices illustrated in the
present disclosure is a semiconductor laser device of a
single-emitter structure which has a single emission region,
although the present invention is not limited to this example. If
each of the semiconductor laser devices includes two or more
emission regions and the emission regions form one or a plurality
of line beams, a semiconductor laser device of a multi-emitter
structure may be used.
[0153] As seen from FIG. 7B, even if the position of each of the
semiconductor laser devices 40 is slightly shifted in the slow axis
direction, a line beam 30L which can be practically used without
difficulty is formed. The tolerance for misalignment in the slow
axis direction of the semiconductor laser devices 40 can be
determined such that a continuous line beam 30L is formed on the
irradiated surface. The misalignment in the slow axis direction of
the semiconductor laser devices 40 is set to, for example, an
amount not more than the size in the slow axis direction of the
emission region 24, Ex.
INDUSTRIAL APPLICABILITY
[0154] A line beam source and a line beam irradiation apparatus of
the present invention can be used for the method of producing an
electronic device, such as LED, flexible display, or the like.
Particularly, a line beam source and a line beam irradiation
apparatus of the present invention can be suitably used for laser
lift-off, although they can also be used for processing of an
object, reforming, melting, crystallization, recrystallization,
cutting, activation of impurities in semiconductor, and
sterilization. A line beam source of the present invention can be
used as a light source for efficiently lighting a plurality of
plants arranged along the same line in a plant factory with light
of a wavelength suitable for photosynthesis.
REFERENCE SIGNS LIST
[0155] 10 semiconductor laser device [0156] 12 p-side electrode
[0157] 16 n-side electrode [0158] 20 substrate [0159] 22
semiconductor multilayer stack [0160] 22a p-side cladding layer
[0161] 22b active layer [0162] 22c n-side cladding layer [0163] 24
emission region [0164] 26a facet (front side) of semiconductor
multilayer stack [0165] 26b upper surface of semiconductor
multilayer stack [0166] 26C facet (rear side) of semiconductor
multilayer stack [0167] 30 laser light [0168] 30C collimated laser
light [0169] 30L line beam [0170] 32 glass substrate [0171] 34
polyimide layer [0172] 34a gap [0173] 36 device [0174] 40
semiconductor laser device (laser diode) [0175] 45 irradiated
surface [0176] 50F fast axis collimator lens [0177] 50S cylindrical
lens [0178] 60 casing [0179] 60a support [0180] 70 controller
[0181] 74 memory [0182] 76 sensor [0183] 76a image sensor [0184]
76b image sensor [0185] 76c image sensor [0186] 80 LD driving
circuit [0187] 90 transporting device driving circuit [0188] 100
line beam source [0189] 200 work stage [0190] 250 transporting
device [0191] 300 work [0192] 400 laser diode array [0193] 410
laser bar [0194] 1000 line beam irradiation apparatus
* * * * *